12 Mayıs 2013 Pazar

Tennessee State Gemstone

Tennessee State Gemstone

Tennessee Pearl

A pearl is organic material made inside the shell of a bivalve such as an oyster, clam, mussel, or abalone. Pearls occur in freshwater and in saltwater. Natural pearls have always been rare, but overharvesting and pollution have made them even more so. Most of the pearls on the market today are cultured pearls, which are also formed by mollusks, but with some human intervention. The process is nearly identical to what happens naturally.
Freshwater pearls are noted for their wide range of colors. They can be found in white, silvery white, pink, salmon, red, copper, bronze, brown, lavender, purple, green, blue, cream, and yellow. Although white is the most common color, the most desirable pearls are in shades of pastel pink, rose, lavender, and purple. The different colors are a function of the mussel species, genetics, water quality, and the position of the pearl in the shell. Generally, pearls assume the color of the shell in which they form. Cultured pearls come in all of the same colors as natural pearls. Black pearls are very rare and for certain reasons cannot be produced with human intervention.
Natural freshwater pearls are seldom perfectly round or even nearly round. The shape of the nucleus and its position in the mussel determines the shape of the cultured pearl. The shapes recovered include round, pear, egg, drop, button, domme, and baroque. In turn, the baroques include many recognized shapes such as nugget, dogtooth, wing, hammer, twin, barrel round-a-circle, and rosebud pearls. The baroque shapes are becoming popular for use in the manufacture of rings, earrings, and pendants.
The Tennessee River Freshwater Pearl Farm is the only freshwater pearl farm in North America. Tennessee also exports various species of Tennessee River mussels to pearl farms in Asia. Tennessee designated the Tennessee River pearl its official state gem in 1979.
Freshwater pearl is also the state gemstone of Kentucky. 
The word pearl comes from the French word perle and the Medieval Latin word perla.
When a foreign substance, such as a grain of sand, a shell fragment, or a parasite, gets lodged between a mollusk’s shell and inner tissues, the organism covers it with a secretion called nacre or mother-of-pearl. Nacre is composed of hexagonal platelets of aragonite, a type of calcium carbonate, which forms in thin layers. This layer of nacre is less than ½ micrometer thick, and is meant to protect the mollusk’s soft tissues from irritants. Over the course of about three to eight years, more layers are laid around the intruding piece of material, forming a hard, white-colored object, known as a pearl.
To produce a cultured pearl, a shell bead or a piece of tissue from another mollusk is inserted inside the shell. This procedure must be done very carefully so that the animal not only survives, but also accepts the material. If successful, the irritant induces the mollusk to secrete layers of brownish protein over the material. The protein is called conchiolin, and is followed by the secretion of numerous thin layers of mother-of-pearl. A cultured pearl is produced in six months to three years.
Processing pearls includes harvesting them from the shells, cleaning and sorting them, treating them in a warm and cold chemical solution called maeshori, and then bleaching the pearls. After bleaching, pearls are drilled and then polished with a mixture of cornmeal and wax. At this stage, pearls are matched into temporary strands, which are matched again into hanks of 5 to 10 for the wholesale trade.
Pearls are harvested from the rivers, streams, and lakes of the eastern, southern, and central United States. To date, 31 U.S. states have reported production of freshwater pearls and shell. During 1993, 18 states reported production, with the bulk of the shell and pearl production coming from Tennessee, Arkansas, Alabama, and Louisiana. North America’s only freshwater pearl farm is located near Camden, Tennessee, and its two saltwater pearl farms are in Hawaii. Freshwater and/or saltwater pearl farms are located in several other countries as well.
  • China
  • Japan
  • United States
  • Australia
  • Indonesia
  • India
  • Sri Lanka
  • Myanmar
  • Philippines
  • Tahiti
Historical uses
Native Americans of the Atlantic coastal areas and the Mississippi River Basin were the first to collect and use U.S. freshwater mussel pearls and shells. Pearl pendants and ear pendants were worn by both sexes and both pearl and shell were used for decorative purposes on articles of clothing. Some of the tribes used pearls as tributes. Reportedly, Powhatan, Pocahontas’ father, had large stores of pearls received as tribute. Additionally, armlets, pendants, and gaming pieces were made from mussel shell.
The fishing and marketing of freshwater pearls and mussel shells by non-Native Americans has a long history in the United States, with the earliest recorded production probably coming from New Jersey. A large shell button industry existed from about the mid-1850s until World War II, when plastic buttons displaced shell buttons.
Modern Uses
Quality of freshwater pearls is determined by the size, color, shape, degree of translucency, texture, ability to match and blend, and iridescence. Because of the wide range of pastel colors, problems can arise in putting together matched strands of freshwater pearls. The U.S. Federal Trade Commission requires that freshwater pearls be referred to as "freshwater cultured pearls" in commerce.
Japan was the first country to cultivate whole freshwater pearls; however, the Japanese freshwater pearl industry is now very limited. The first experimental freshwater cultured pearl farm in the U.S. was established in Tennessee by the late John Latendresse in 1963. Latendresse is considered the father of American cultured freshwater pearls, having spent more time, money, and effort than anyone else in the research and development of the industry. The future of the industry will depend on the availability of pollution-free water suitable for a pearl farm and on the public demand for cultured pearls.
Early Chinese myths told of pearls falling from the sky when dragons fought. Ancient legend says that pearls were the tears of the gods. Greeks believed that wearing pearls would promote marital bliss. Pearls are believed to reduce stress and its resulting maladies: hypertension, headaches, and exhaustion. Pearls are also thought to aid in digestion and reduce the chance of developing ulcers. 
Pearl is the modern birthstone for those born in June and the birthstone for zodiac signs Gemini and Cancer. Freshwater pearls are given on the first wedding anniversary. Pearls are suitable gifts for the third, 12th, and 30th anniversaries.
State Gemstone
Rough Pearls in the Shell
State Gemstone
Grafting Pearls
State Gemstone
Sorted Freshwater Pearls
State Gemstone
Polished Pearls in Varying Sizes
State Gemstone
Pearl Strands
Group: Pearl
Crystal Structure: Microcrystalline
Hardness (Mohs): 4
Color: Varying; commonly pink, white or black
Transparency: Opaque
Luster: Varying 
Pleochroism: None
Refractive Index: 1.52-1.69
Density: 2.60-2.78
Cleavage: None

Some data courtesy of the Mineralogical Society of America
Author: World Trade Press

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